tolkiens legendarium - Does the tone of The Hobbit significantly differ from that of Lord of the Rings?

I'm rapidly approaching the conclusion of The Return of the King, and next on my list is The Hobbit. This is my first time reading Tolkien, and I have been putting it off for 24 years. I'm a little concerned about moving on to The Hobbit, which was written for children, more or less, after spending so much time in the more adult-oriented world of LotR.

Am I going to be disappointed by the relative lightness of The Hobbit, as compared to LotR? Does the tone, or mood, of The Hobbit differ significantly from the fairly dark tone/mood of LotR? If there is a substantial difference, am I correct in assuming that The Hobbit is lighter, less serious, and more family-friendly? I really don't want this to be a comedown.

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Note: I don't think that this question is opinion based- I believe Tolkien wrote about the challenges of linking the two stories together, in light of the fact that The Hobbit was a children's story whereas LotR definitely is not. I am just wondering if the difference is as noticeable as he seemed to believe, and exactly what the difference is. If the question is closed, however, I will understand. I had reservations about asking it in the first place.

Answer

Words of Tolkien himself (source):

My work did not 'evolve' into a serious work. It started like that. The so-called 'children's story' was a fragment, torn out of an already existing mythology. In so far as it was dressed up as 'for children,' in style or manner, I regret it. So do the children.

And the same source states that he started out as a "writer of children's books".

Dramatic changes in his writing style had occurred by the time he came to write Lord of the Rings - to the extent that he would have like to overhaul The Hobbit and rewrite it in the same style as Lord of the Rings.

Carpenter's biography, as quoted here, tells us:

[Tolkien] found The Hobbit to be "very poor" (according to Humphrey Carpenter's biography). There are glimpses of Tolkien's dissatisfaction with The Hobbit in some of his letters. He felt he was too condescending to children in the early part of the book, and he would have preferred to rewrite it completely, had there been time to do so.

Having not got Carpenter's biography to hand, I can't provide a first-hand quote, but maybe someone who has could provide it...

Excellent summary of The Hobbit here, which tells us:

The Hobbit was originally a story Tolkien told to his children. [...] It is described as a fantasy novel, a story of heroic quest, and a children's story.

The narrator and the tone of the narration are sometimes comic, and sometimes condescending to the reader. This condescension was not unusual in books for children in the early 20th century.

Basically, the answer is yes.

Every serious Tolkien fan would agree.

Relevant: this SFF.SE question and its answers.